1. Field of the Invention
The present invention relates to a data communication system, and in particular to a data transmitting method and a data receiving method as well as a data transmitting apparatus and a data receiving apparatus applied to all wireless network environments regardless of a network configuration or a protocol.
2. Description of the Related Art
A connection-type communication using an Ack response (delivery acknowledgement) (hereinafter, occasionally referred to simply as “Ack”) frame has been performed to acknowledge that a communication has been normally done to a next wireless terminal (node). Such a communication will be described hereinafter referring to FIGS. 10 and 11.
Firstly, as shown in FIG. 10, a wireless terminal 10 is composed of a transmission controller 20 and a reception controller 30, these controllers 20 and 30 being mutually connected. The transmission controller 20 is composed of an Ack request controller 40 for controlling the transmission of an Ack request, an Ack response controller 50 for controlling the transmission of an Ack response, and a retransmission controller 60 for retransmitting a transmitted frame when the transmitted frame has not reached the next terminal. Also, the reception controller 30 is composed of an Ack request monitoring portion 70 for detecting an Ack request from a received frame and an Ack reception monitoring portion 80 for detecting an Ack response for a transmitted frame.
FIG. 11 shows an example of a data communication using such a wireless terminal, where it is supposed that a wireless terminal 10a is a node on a data transmitting side and a wireless terminal 10b is a node on a data receiving side.
When trying to transmit data between the wireless terminals 10a and 10b, at a transmission request generated in the wireless terminal 10a, the wireless terminal 10a transmits a data frame DATA addressed to the wireless terminal 10b (at steps S101 and S103). In the instant data frame DATA, an Ack request is included by the Ack request controller 40.
Therefore, in response to the data frame DATA in the wireless terminal 10b, the Ack request monitoring portion 70 extracts the Ack request from the received data frame DATA, the Ack response controller 50 in the transmission controller 20 transmits an Ack response to the wireless terminal 10a (at steps S102 and S104). Thus, the Ack reception monitoring portion 80 within the reception controller 30 in the wireless terminal 10a recognizes the Ack response as that for the transmitted data frame DATA, whereby the transmission is completed.
Also, when the wireless terminal 10a transmits the data frame DATA (at step S105), and an Ack response thereto is not returned within a fixed time (Ack waiting timeout period To) (at step S106), the data frame DATA is recognized as not having reached the wireless terminal 10b (undelivered), so that the retransmission controller 60 in the transmission controller 20 of the wireless terminal 10a retransmits the data frame DATA (at step S107).
In return, when the wireless terminal 10b provides the wireless terminal 10a with the Ack response (at step S108), the data frame DATA is subsequently transmitted from the wireless terminal 10a to the wireless terminal 10b (at step S109) in the same way as in the above-mentioned steps S101-S104, so that the Ack response is returned (at step S110).
On the other hand, there is a communication system and a communication control method where a wireless base station evaluates a transmission quality of the wireless communication passage between the wireless base station and the wireless terminal based on transmitting/receiving sate of down data and a response for the down data, transmits information showing an evaluated result to a wireless network controller as feedback information, and the wireless network controller controls a communication parameter of each layer to be performed between the wireless network controller and the wireless terminal based on the feedback information (see e.g. patent document 1).
[Patent document 1] Japanese Patent Application Laid-open No. 2003-319458
The prior art example shown in FIGS. 10 and 11 establishes a highly reliable communication by using an Ack response for data frame for every transmission of the data frame. However, since the Ack response is transmitted for each of the data frames, a reduction of data transfer efficiency due to a transmission occupation time of the Ack response and an increase in traffic over the network for the portion of the Ack response occur, so that effective use of resources is obstructed, which becomes a significant problem especially under a network (radio wave) environment having a lot of relaying wireless terminals as data transfer amount increases in a network.